SLP528 Neurology
Guide to neurology for clinicians and students in speech-language pathology
Speech Perception
Bottom-up and Top-down processing
There are different ways of perceiving what we hear (or read) every day.
Bottom-up processing refers to the cognitive process of hearing something and understanding what you are hearing. It is simplistic and based on what you know.
Top-down processing refers to the cognitive process of using your knowledge of the language to fill in any possible gaps.
We probably use top-down processing more than you think!
As soon as you looked at this picture from Wheel of Fortune, you probably filled in that the missing word was PAINTED. We can tell because of our knowledge of the language. No other word would make sense there given we know it’s a landmark.
Everyday examples of Top-down processing in action:
*Your cell signal is bad or you’re in a noisy room so you fill in bits or words you didn’t quite hear.
*A boy introduces himself to you as “Mike.” Even if you didn’t really hear him say the “m” you can assume the correct name since there’s no other male name like it.
You are able to guess based on context and your own knowledge!
To exercise your top-down processing even more, head over here for some hangman!
Perceiving Foreign Sounds
Have you ever had trouble understanding a foreign language?
Did the words sound completely unfamiliar to you?
Don’t worry! You are not alone.
In a study conducted by Winkler et al. (1999), they studied the perception of phonemes in 3 different groups:
1. Finns who spoke only Finnish
2. Hungarians who spoke Hungarian and Finnish
3. Hungarians who spoke only Hungarian
The Hungarians who only spoke Hungarian were less able to tell the difference between Finnish sounds. Why? Because non-native speakers will have difficulty processing unfamiliar sounds.
Think about it: The less familiar you are with a sound, the less likely you will be able to identify it.
Feedforward and Feedback Loops in Speech Processing
When we think about speech perception, we often think of perceiving others' speech. However, we are constantly monitoring our own speech as well!
SPEECH SOUND MAP: The "map" we create in our heads that tells us the sequence of the word we want to say. For example, we know to say "cat," the phonemes must be in this order: /k/ /æ/ /t/.
FEEDFORWARD SYSTEM: While you're saying a word, the auditory cortex makes a connection with the "map" about what the word should sound like.
AUDITORY ERROR MAP: This is the idea that we've had a possible slip of the tongue and we perceive our mistake. For example, saying "rat" instead of "cat!"
SOMATOSENSORY ERROR MAP: We not only hear what we are saying, but we can feel it too with our articulators. Say the words "rat" and "cat" to yourself. Notice how your tongue is positioned differently for "r" and "c."
Sensorimotor Control in Speech Perception
According to Hickok and Poeppel (2007) we have two streams of speech and language processing:
1. The ventral stream: perceiving speech
2. The dorsal stream: monitoring the speech we are producing
Speech perception is not a passive task! We are constantly thinking about what words sound like and collecting information from other senses to figure out what words mean.
To read their original research: